Modeling CVD diamond with density functional theory

Abstract

Chemical vapor deposition (CO) of polycrystalline flms of diamond has improved dramatica1.y during the past six years. During this time there have been parallel developments in modeling chemical processes at a diamond surface, with many of the first-principle studies being carried out within the density functional framework. We review our work on furthering the understanding of chem:cal processes that may be important in the growth process, which requires knowledge of first, the surfaces themselves and second, adsorption of hydrocarbon radicals to add more layers. Studies of both clean and hydrogenated ( 111). (IOO), and (110) surfaces of diamond show that clean surfaces tend to undergo strong relaxation and reconstruction while hydrogenation results in inen surfaces. Modeling interactions of various hydrocarbon radicals with diamond surfaces provides energies and geometries of viable processes while eliminating from furlher consideration processes that are found to be unfavorable. We also discuss briefly recent investigation of behavior at a step on a clean diamond surface, which may indicate a process leading to graphitization of the diamond surface.

Diamond Nucleation on Hexagonal Boron Nitride: A Theoretical Investigation of the Influence of Nearest Substituents

“…The calculations in the present investigation show that the presence of H, or the electronegative species F and OH, does not substantially alter the diamond stabilization energy (or the atomic charges). This is in contrast to earlier investigations where growth processes on diamond surfaces were studied. − For instance, the adsorption of a growth species (CH 3 ), being the first step in a nucleation process, was found to be influenced differently by neighboring surface-bonded F vs H species…”

“…The latter will influence by introducing steric hindrances. The influence of electronegative differences on, for example, adsorption and nucleation on H- and F-terminated diamond surfaces has earlier been investigated theoretically. − Charge transfer from the surface, and specific adsorbates, to the electronegative terminating F species was then also discussed. No corresponding withdrawing effect was observed when terminating the surface with H atoms.…”

“…This is in contrast to earlier investigations where growth processes on diamond surfaces were studied. [34][35][36] For instance, the adsorption of a growth species (CH 3 ), being the first step in a nucleation process, was found to be influenced differently by neighboring surface-bonded F vs H species. 34 Both the adsorption energy and the total atomic charges close to the structural region of adsorption varied.…”